1. Field of the Invention
The present invention relates to the removal of contaminants from industrial used lubricating oils and used motor oils by treatment of the used oil with clay at high temperatures, but at lower temperatures than that of “cracking”, and later removing the contaminated clay by filtration and centrifugation.
2. Description of the Prior Art
The recycling of used lubricating oils coming from industrial processes, car motors, transmissions and other sources is an important process, because it avoids contamination by lubricating oils, and allows the recovery of lubricating base oils, which are a scarce product. The oils form a mono-molecular layer on the surface of the water, which it means that a small quantity of oil can contaminate a great volume of water.
The recovered lubricating oil bases have all the properties of the first refining, and they can be used to produce new oils. The recycling process can be done several times.
The contaminants in industrial oils, besides water, are usually iron, chromium, cadmium, nickel, copper, calcium, barium, zinc, aluminum, and phosphorus. Motor oils also have soot, contaminants due to degraded additives, and other contaminants coming from the gasoline, and for that reason they are more difficult to be re-refined.
Several techniques have been used to re-refine used oils, mainly by distillation and treatment with chemical reactives to precipitate the coagulants (principally sulfuric acid and other solvents, which are also contaminants that produce environmental problems).
The treatments with clays at very high temperature have the problem that the later separation becomes difficult because the pores of the felt (cloths, cellulose, synthetic materials or others) of the filter press become plugged, mainly due to soot, colloidal coal, and organic compounds.
The distillation systems require large investments, and the re-refining cost is usually expensive. This is also the case of the other used treatments with sulfuric acid, sulfates, phosphates and other chemicals, which are difficult to extract later on. For example in the separation of sulfuric acid with clays there is the inconvenience of the great production of sludge, besides the large volumes of corrosive acids and the great lost of used original oils. It is necessary to take into account that the pre-heating of the mixtures must not be higher than 250° C. to 300° C., if one wants to avoid the “cracking” of the lubricating oils. (Excessive heat causes hydrocarbon chains in the oil to “crack” and break into smaller chains, which are not suitable for lubricating oil, though they may be suitable for fuel oil.) Other more economic systems use inorganic catalysts mixed with clays in continuous feeding systems.
U.S. Pat. No. 3,625,881, issued on Dec. 7, 1971, to John M. Chambers and Herbert A. Hadley, discloses a process for reclaiming lubricating oils, including flash vaporization to remove water, mixing the used oil with a hydrocarbon oil, using a centrifuge to remove solid precipate, and two fractional distillations. The instant invention is distinguishable, in that in it the used oil is mixed with clay rather than another oil.
U.S. Pat. No. 3,639,229, issued on Feb. 1, 1972, to Darrell W. Brownawell and Remi H. Renard, discloses a process of refining used lubricating oils, in which the used oil is mixed with aliphatic alcohol. There may be a final clay treating step (see claim 9). The instant invention is distinguishable, in that it does not require the use of alcohol.
U.S. Pat. No. 3,819,508, issued on Jun. 25, 1974, to Morton Fainman and Charles Stouse McCauley, discloses a method of purifying lubricating oils, in which the oil is mixed with a predominantly hydrocarbon liquid diluent, then with an alcohol and water mixture, and centrifuging is used to remove sludge and metal compounds. The instant invention is distinguishable, in that in it the used oil is mixed with clay.
U.S. Pat. No. 3,919,076, issued on Nov. 11, 1975, to Louis E. Cutler, discloses a process for re-refining used automotive lubricating oil, including treatment with a saturated hydrocarbon solution, followed by vacuum distillation, followed by catalytic hydrogenation, which are not required in the instant invention.
U.S. Pat. No. 3,930,988, issued on Jan. 6, 1976, to Marvin M. Johnson, discloses a process for reclaiming used motor oil using an aqueous solution of ammonium sulfate or bisulfate, that is not required in the instant invention.
U.S. Pat. No. 4,033,859, issued on Jul. 5, 1977, to Donald Douglas Davidson and Bjorn I. Engesvik, discloses thermal treatment of used petroleum oils under pressure at temperatures to above about 400 to 800 degrees Fahrenheit (or 190 to 412 degrees Celsius). Although there may be a small overlap in the temperature range, the instant invention does not require pressure during its heating step.
U.S. Pat. No. 4,383,915, issued on May 17, 1983, to Conrad B. Johnson, discloses a clay contacting process for removing contaminants from waste lubricating oil, in which the oil is contacted with decolorizing clay at a temperature in the range of 650 to 725 degrees Fahrenheit (or 329 to 370 degrees Celsius). The instant invention is distinguishable, in that it uses a lower temperature range.
U.S. Pat. No. 4,502,948, issued on Mar. 5, 1985, to Donald C. Tabler, discloses a procedure for treating demetallized used oil using an acid such as sulfuric acid. In the instant invention, no sulfuric or other acid is used.
U.S. Pat. No. 5,112,479, issued on May 12, 1992, to Vichai Srimongkolkul, discloses an oil purification unit with a cyclonic (centrifuge) reservoir section and a filtration section. The second embodiment of the instant invention is distinguishable, in that in it the oil is first mixed with clay before being centrifuged.
U.S. Pat. No. 5,288,413, issued on Feb. 22, 1994, to Humbert H. Chu, discloses treatment of a waste sludge to produce a non-sticking fuel, using a vacuum or pressure, neither of which are required by the instant invention.
U.S. Pat. No. 5,759,385, issued on Jun. 2, 1998, to Marcel Aussillous et al., discloses a process and plant for purifying spent oil, including vacuum distillation, which is not required by the instant invention.
U.S. Pat. No. 5,968,370, issued on Oct. 19, 1999, to Mark E. Trim, discloses a process for removing hydrocarbons bound to solid particles in contaminated sludge, such as from oil refineries, supertankers, and drill cuttings. A treatment fluid is applied, comprising water, a silicate, a nonionic surfactant, an anionic surfactant, a phosphate builder and a caustic compound. Later, the treatment fluid is removed, to be used again. In the instant invention, the products to be treated are different, namely lubricating oils contaminated with small amounts of metals and other products, as a result of their use as lubricants. In the instant invention, only clay is used; no fluid treatment is used, and no treatment fluid is recovered, but only the lubricating oils themselves.
U.S. Patent Application Publication No. 2002/0166794, published on Nov. 14, 2002, to Alexander P. Bronhstein, Moshe Gewertz and Vladimir M. Rozhansky, discloses a process for producing standard and used fuels from lubricating oils and several other waste products. It produces a mixture of water and other products to be added to petroleum-based waste. Later, dewatered matter is skimmed, and what remains is processed by thermocatalytic cracking. The instant invention produces a lubricating oil basis (not fuel) from used lubricating oils. In the instant invention, no water as a carrier of products is used. Instead, most of the water is taken out by methods such as decanting and heating, before treatment with clay in the reactor. In the instant invention, no skimming of a watered mixture is performed, nor is thermocatalytic cracking used, thus it has a final product different from that of Bronhstein et al. Instead of fuel products, it obtains a lubricating oil basis, which can be used to obtain new lubricating oil by adding appropriate additives.
U.S. Patent Application Publication No. 2006/0000787, published on Jan. 5, 2006, to Louis Galasso III et al., discloses purification of impure oil by centrifugation, without first mixing the oil with clay as in the instant invention.
Japanese Patent No. 2-4898, published on Jan. 9, 1990, to Kyoho Seisakusho and Toyota Jidosha, discloses a process of reclaiming lubricating waste oil, including a thermal reaction treatment in which an aqueous solution of caustic alkali is added to the oil, a centrifugation process after diatomaceous earth and activated clay are added to the oil, and a filtration process. The instant invention is distinguishable, in that it does not require that the addition of a solution of caustic alkali to the oil.
French Patent No. 2 690 924, published on Nov. 12, 1993, to Virgulino Antonio Digilio, discloses a method of re-cycling of used or contaminated lubricating oils, including adding clay to the oil in a reactor, and also adding water containing a dissolved sulfur based catalyst and filtration aid. The instant invention is distinguishable, in that it does not require adding water containing a catalyst. Dr. Pablo Martin de Julian, the first named inventor herein, has corrected the machine translation provided by the Examiner in the parent application, and this corrected translation is submitted with the present application.
Page 10, lines 4-5 of the English translation of Digilio submitted herewith states that it uses “a catalyst based in diluted active sulfur and the addition approximately 2% of auxiliary of filtration, such as the diatomite”, but the present invention does not use any of these things. Likewise, in Tabler (U.S. Pat. No. 4,502,948 supra), sulfuric acid is added to the oil.
The process of centrifugation in the present invention is fundamentally different from the process of centrifugation disclosed in Digilio. The present invention uses a centrifuge to separate clay that has absorbed soot (i.e., colloidal hydrocarbons) from the rest of the mixture comprising oil and clay that has absorbed other contaminants (e.g., metals). Page 8, lines 35-36 of the English translation states that centrifugation “eliminates a considerable quantity of water before containing dissolved salts, carbon deposits and nonsoluble sediments.” Because of this important difference between these processes, the stage where centrifugation is performed is also different. In Digilio, centrifugation is performed at the beginning, while in the present invention it is performed near the end before the filter press procedure. In the present invention, centrifugation is performed with the mixture of oil, clay and contaminants, while in Digilio the contaminated oil is centrifuged before the clay is added.
In summary, the main differences between the present invention and the prior art are as follows:
In the process of the present invention, the decontamination with the clay is performed in an open reactor at atmospheric pressure. In contrast, Digilio has to use an autoclave, because he has to work with a high pressure of 58.8399×104 to 98.0665×104 Pascals in part of the process, and also to use a partial vacuum by applying from time to time a low pressure of 7.3326×104 Pascals (see page 10, line 13 of the English translation and page 12, lines 33-34 of the original French). The process of the present invention is both simpler and less expensive, because autoclaves are much more expensive than open reactors.
In the present invention, the clay used to decontaminate the used lubricating oil acts on the oil free of water, as any water in the original used oil is removed by the flash distillation before the clay is put in contact with the oil and its contaminants, and water is never added. By contrast, in Digilio, water with “a catalyst based in diluted active sulphur” and an “auxiliary of filtration, such as the diatomite” is added to the oil and clay (see page 10, lines 3-4 of the English translation). This is critical, because the efficiency of the clay in decontaminating is much greater when the oil is free from water, and decreases rapidly when water is present.
Clay Amended Soilless Substrates: Increasing Water and Nutrient Efficiency in Containerized Crop Production by James Stetter Owen, Jr. (2006) does not disclose the use of clay for cleaning used lubricating oils, as in the instant invention.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.
We can summarize the prior art process for recovering used lubricating oil as having three parts or stages:
First there is the adaptation or preparation process, which consists in the separation of solids and water, usually by filtration and flash distillation, respectively, or other process.
In a second stage there is a treatment to eliminate the contaminant products, such as metals, soot, organic refuse, additives, oligogenic compounds, etc. This elimination process is done: i) by chemical methods, such as adding sulfuric acid, calcium sulfate, hydroxides, phosphoric acid, etc.; ii) by physical-chemical methods as vacuum distillation; or iii) by other methods.
The third stage is the process of whitening and taking out the smell. Here there are also use different methods, but the most common is the use of clay or activated carbon.
The present invention has important advantages with respect to these processes.